The present invention relates generally to the field of photoresist compositions. In particular, the present invention relates to polymer compositions useful in photoresist compositions.
Photoresists are photosensitive films used for transfer of images to a substrate. A coating layer of a photoresist is formed on a substrate and the photoresist layer is then exposed through a photomask to a source of activating radiation. The photomask has areas that are opaque to activating radiation and other areas that are transparent to activating radiation. Exposure to activating radiation provides a photoinduced chemical transformation of the photoresist coating to thereby transfer the pattern of the photomask to the photoresist-coated substrate. Following exposure, the photoresist is developed to provide a relief image that permits selective processing of a substrate.
A photoresist can be either positive-acting or negative-acting. For most negative-acting photoresists, those coating layer portions that are exposed to activating radiation polymerize or cross-link in a reaction between a photoactive compound and polymerizable agents of the photoresist composition. Consequently, the exposed coating portions are rendered less soluble in a developer solution than unexposed portions. For positive-acting photoresists, exposed portions are rendered more soluble in a developer solution while areas not exposed remain comparatively less developer soluble. In general, photoresist compositions include at least a resin binder component and a photoactive agent.
More recently, chemically-amplified type resists have been increasingly employed, particularly for formation of sub-micron images and other high performance applications. Such photoresists may be negative-acting or positive-acting and generally include many cross-linking events (in the case of a negative-acting resist) or deprotection reactions (in the case of a positive-acting resist) per unit of photogenerated acid. In the case of positive chemically-amplified resists, certain cationic photoinitiators have been used to induce cleavage of certain xe2x80x9cblockingxe2x80x9d groups pendant from a photoresist binder, or cleavage of certain groups comprising a photoresist binder backbone. See, for example, U.S. Pat. Nos. 5,075,199; 4,968,581; 4,810,613; and 4,491,628 and Canadian Patent Application 2,001,384. Upon cleavage of the blocking group through exposure of a coating layer of such a resist, a polar functional group is formed, e.g. carboxyl or imide, which results in different solubility characteristics in exposed and unexposed areas of the resist coating layer. See also R. D. Allen et al. Proceedings of SPIE, 2724:334-343 (1996); and P. Trefonas et al. Proceedings of the 11th International Conference on Photopolymers (Soc. of Plastics Engineers), pp 44-58 (Oct. 6, 1997).
While currently available photoresists are suitable for many applications, current resists can also exhibit significant shortcomings, particularly in high performance applications such as formation of highly resolved sub-half micron and sub-quarter micron features.
Consequently, interest has increased in photoresists that can be photoimaged with short wavelength radiation, including exposure radiation of about 250 nm or less, or even about 200 nm or less, such as wavelengths of about 248 nm (provided by a KrF laser), 193 nm (provided by an ArF exposure tool) or 157 nm. Use of such short exposure wavelengths can enable formation of smaller features. Accordingly, a photoresist that yields well-resolved images upon 248, 193 or 157 nm exposure could enable formation of extremely small (e.g. sub-quarter micron) features that respond to constant industry demands for smaller dimension circuit patterns, e.g. to provide greater circuit density and enhanced device performance.
Current photoresist compositions include one or more polymeric binders, optionally a cross-linking agent and a photoactive component. The polymeric binders are typically linear polymers having relatively low molecular weights, such as up to 20,000 Daltons. Such polymeric binders are desired as they tend to form coatings of uniform thickness and can be easily dispensed onto a substrate for lithographic processing. When photoresists containing such linear polymers are used in nanolithographic (i.e. under 200 nm) processes, line edge roughness is often difficult to control. When conventional photoresists containing acrylate-based polymeric binders are used, the resulting exposed resist cannot be developed using conventional tetraalkylammonium hydroxide based developers, but instead require very dilute tetraalkylammonium hydroxide based developers or other developers such as carbonate. Such developers tend to swell acrylate-based polymers, which adversely affects the imaged feature size, adhesion to the substrate, linewidth, line development and collapse of the feature.
Other forms of polymeric binders, such as polymer particles, have not been used as binders in photoresist compositions. Such polymer particles have been thought difficult to dispense to provide a uniform coating on a substrate, difficult to image and highly prone to defects.
Thus, there is a continuing need for photoresists, particularly for nanolithographic processes, that have reduced or controllable line edge roughness.
It has been surprisingly found that polymeric particles are effective as binders in photoresist compositions. It has also been surprisingly found that certain polymeric, particle binders, such as fluorinated polymeric particles, are particularly effective for use in photoresist compositions for imaging at sub-200 nm wavelengths, such as 157 nm.
In one aspect, the present invention provides a photoresist composition including a plurality of cross-linked polymeric particles and a photoactive component, wherein the polymeric particles include one or more cleavable groups and wherein the composition is substantially free of surfactant.
In a second aspect, the present invention provides a method for forming a photoresist relief image, including the steps of applying a coating layer of a photoresist composition including a plurality of cross-linked polymeric particles and a photo active component, wherein the polymeric particles include one or more cleavable groups and wherein the photoresist composition is substantially free of a surfactant; exposing the photoresist coating layer to patterned activating radiation; and developing the exposed photoresist coating layer to provide a photoresist relief image.
In a third aspect, the present invention provides a plurality of core-shell polymeric particle comprising one or more photoactive components as core-material.
In a fourth aspect, the present invention provides a photoresist composition including a plurality of core-shell polymeric particles and a photo active component, wherein the polymeric particles include one or more cleavable groups.
In a fifth aspect, the present invention provides a method for forming a photoresist relief image, including the steps of applying a coating layer of a photoresist composition including a plurality of core-shell polymeric particles and a photoactive component, wherein the polymeric particles include one or more cleavable groups; exposing the photoresist coating layer to patterned activating radiation; and developing the exposed photoresist coating layer to provide a photoresist relief image.
In a sixth aspect, the present invention provides a photoresist composition including a plurality of cross-linked polymeric particles and a photoactive component, wherein the polymeric particles include one or more cleavable groups and wherein the composition is substantially free of solvent.
In a seventh aspect, the present invention provides a method for manufacturing an electronic device including the steps of disposing on the surface of a substrate a photoresist composition including a plurality of cross-linked polymeric particles and a photoactive component, wherein the polymeric particles include one or more cleavable groups and wherein the photoresist composition is substantially free of surfactant; exposing the photoresist coating layer to patterned activating radiation; and developing the exposed photoresist coating layer to provide a photoresist relief image.
In an eighth aspect, the present invention provides a method for manufacturing an electronic device including the steps of disposing on the surface of a substrate a photoresist composition including a plurality of core-shell polymeric particles and a photoactive component wherein the polymeric particles include one or more cleavable groups; exposing the photoresist coating layer to patterned activating radiation; and developing the exposed photoresist coating layer to provide a photoresist relief image.
In a ninth aspect, the present invention provides a photoresist composition including a plurality of cross-linked solution polymer particles and a photoactive component, wherein the polymer particles include one or more cleavable groups.